+/**
+ * Return the content type for specified feed type.
+ *
+ * @since 2.8.0
+ */
+function feed_content_type( $type = '' ) {
+ if ( empty($type) )
+ $type = get_default_feed();
+
+ $types = array(
+ 'rss' => 'application/rss+xml',
+ 'rss2' => 'application/rss+xml',
+ 'rss-http' => 'text/xml',
+ 'atom' => 'application/atom+xml',
+ 'rdf' => 'application/rdf+xml'
+ );
+
+ $content_type = ( !empty($types[$type]) ) ? $types[$type] : 'application/octet-stream';
+
+ /**
+ * Filter the content type for a specific feed type.
+ *
+ * @since 2.8.0
+ *
+ * @param string $content_type Content type indicating the type of data that a feed contains.
+ * @param string $type Type of feed. Possible values include 'rss2', 'atom'.
+ * Default 'rss2'.
+ */
+ return apply_filters( 'feed_content_type', $content_type, $type );
+}
+
+/**
+ * Build SimplePie object based on RSS or Atom feed from URL.
+ *
+ * @since 2.8.0
+ *
+ * @param mixed $url URL of feed to retrieve. If an array of URLs, the feeds are merged
+ * using SimplePie's multifeed feature.
+ * See also {@link ​http://simplepie.org/wiki/faq/typical_multifeed_gotchas}
+ *
+ * @return WP_Error|SimplePie WP_Error object on failure or SimplePie object on success
+ */
+function fetch_feed( $url ) {
+ require_once( ABSPATH . WPINC . '/class-feed.php' );
+
+ $feed = new SimplePie();
+
+ $feed->set_sanitize_class( 'WP_SimplePie_Sanitize_KSES' );
+ // We must manually overwrite $feed->sanitize because SimplePie's
+ // constructor sets it before we have a chance to set the sanitization class
+ $feed->sanitize = new WP_SimplePie_Sanitize_KSES();
+
+ $feed->set_cache_class( 'WP_Feed_Cache' );
+ $feed->set_file_class( 'WP_SimplePie_File' );
+
+ $feed->set_feed_url( $url );
+ /** This filter is documented in wp-includes/class-feed.php */
+ $feed->set_cache_duration( apply_filters( 'wp_feed_cache_transient_lifetime', 12 * HOUR_IN_SECONDS, $url ) );
+ /**
+ * Fires just before processing the SimplePie feed object.
+ *
+ * @since 3.0.0
+ *
+ * @param object &$feed SimplePie feed object, passed by reference.
+ * @param mixed $url URL of feed to retrieve. If an array of URLs, the feeds are merged.
+ */
+ do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );
+ $feed->init();
+ $feed->set_output_encoding( get_option( 'blog_charset' ) );
+ $feed->handle_content_type();
+
+ if ( $feed->error() )
+ return new WP_Error( 'simplepie-error', $feed->error() );
+
+ return $feed;
+}